Sheet coating machine

ABSTRACT

A sheet coating machine in which sheets are fed along a bed through a working area where they are given a coating of a volatile substance to an adjoining oven where the coating is cured. At least one cover is moveable to provide access when necessary to the working area and which enables vapors produced by evaporation from the substance to be contained within the working area. Air inlet means enable the vapors to be extracted for incineration, and suction means which are arranged to extract the vapors downwardly from within the working area.

This invention relates to sheet coating machines, that is to say tomachines for coating sheets with a variety of substances most of whichinclude high quantities of volatile organic solvents which areevaporated off and incinerated during a following curing process in athermal drying oven. However, very significant amounts of solventvapourise at the machine, and health and safety regulations require thatthese are not dissipated into the atmosphere but are incinerated.

It is well known to enclose the coating machine entirely within a frontextension of the oven, thus containing the solvent emissions from themachine within the oven. However, this arrangement has the disadvantagesthat the atmosphere within the extension must be acceptable to anoperator working therein for the purposes of setting and checking themachine, but the size of the extension requires that a high rate of airflow into it is needed to keep the atmosphere acceptable, which in turnlowers the thermal efficiency of the oven; and that machine elements andcoating substances have to be transported into and handled within theconfines of the extension.

It is also known to enclose the coating machine entirely within asizeable chamber separate from the oven, to provide a tunnel connectingthe chamber and the oven through which the sheets are transported, andto provide an extraction system for the chamber. This arrangementsuffers from the same disadvantages as the arrangement referred to inthe preceding paragraph.

There has also been produced hitherto a coating machine with a hoodabove it enabling vapours to be contained within the working area andhaving two covers which could be raised to provide access to said area.An extraction system was mounted above the machine on or adjacent to thehood between the covers, drawing the vapours upwardly. This arrangementhas the disadvantages that the hood and the extraction system hinder theinstallation and use of a hoist for enabling machine elements to bechanged; that extraction is less effective because the vapours areheavier than air; and that during setting and checking of the machinewhen one or both of the covers is or are raised and the extractionsystem is still in operation, vapours are drawn upwardly past the headof the operator.

The object of the present invention is to avoid all of the disadvantageshereinbefore referred to.

The invention comprises a sheet coating machine in which sheets are fedalong a bed through a working area where they are given a coating of avolatile substance to an adjoining oven where the coating is cured, atleast one cover which is moveable to provide access when necessary tothe working area and which enables vapours produced by evaporation fromthe substance to be contained within the working area, air inlet meanswhich enable the vapours to be extracted for incineration, and suctionmeans which are arranged to extract the vapours downwardly from withinthe working area.

The working area preferably comprises a coating station having amoveable cover which provides access when necessary to the coatingstation.

Preferably, the air inlet means of the coating station comprise vents inthe moveable cover.

Preferably, also, the coating station is provided with a base, wallsalong its sides, and upstream and downstream baffle plates across itsends in order to contain the vapours within the coating station, thebaffle plates being adapted to permit feeding of the sheets along thebed.

Preferably, the working area comprises also a sheet reject stationdisposed between the coating station and the oven and having anothermoveable cover which provides access when necessary to the sheet rejectstation.

Preferably, also, the sheet reject station is provided with a floor,walls along its sides, and upstream and downstream baffle plates acrossits ends in order to contain the vapours within the sheet rejectstation, the baffle plates being adapted to permit feeding of the sheetsalong the bed.

Preferably, the walls of the sheet resect station are continuations ofthe walls of the coating station, and the upstream baffle plate of thesheet reject station and the downstream baffle plate of the coatingstation are one and the same element.

Preferably, also, the air inlet means of the sheet reject stationcomprise vents in a reject sheet withdrawal door in one of the walls.

Preferably, the suction means which are arranged to extract the vapoursdownwardly comprise ducts connected to the base of the coating station,to the sheet reject station, to a gearbox for driving the machine, andto a housing for a replaceable tank from which the substance is suppliedto the coating station.

Preferably, also, the ducts communicate with a common duct in the baseof the machine leading to an upper zone of the oven.

The sheet coating machine is preferably provided with a hoist forenabling machine elements to be changed which is disposed above theworking area and is completely unimpeded by the suction means which arearranged to extract the vapours downwardly.

A preferred embodiment of the invention will now be described, by way ofexample, with reference to the accompanying drawings on different scalesof which:

FIG. 1 shown in two parts 1A and 1B is a side elevation of a sheetcoating machine with an adjoining sheet supplying mechanism shown inbroken lines at its right hand end and an adjoining oven shown in brokenlines at its left hand end;

FIG. 2 shown in two parts 2A and 2B is a plan view the machine with saidmechanism shown in broken lines but with the oven omitted;

FIG. 3 is a cross-section on the line 3—3 in FIG. 1 with parts omittedfor clarity;

FIG. 4 is a side elevation of means for pivotally raising the cover ofthe coating station;

FIG. 5 is a plan view of said cover included to show some of themachine's extraction ducts disposed beneath it in the base of thecoating station; and

FIG. 6 is a diagrammatic drawing showing the machine's suction means insectional side elevation.

Referring now to the drawings, a sheet coating machine, an adjoiningsheet supplying mechanism therefor and an adjoining thermal drying oventherefor are indicated generally at 10, 12 and 14 respectively. Themachine 10 has a flat bed 16 along which sheets are fed by conveyormeans 17 and 19 through a working area comprising a coating stationindicated generally at 18 where they are given a coating of a volatilesubstance such as lacquer and, downstream of the coating station 18, asheet reject station indicated generally at 20 which allows a sheet tobe withdrawn from the bed 16 for inspection. From the sheet rejectstation 20 the sheets normally pass to the oven 14 where the coating iscured. The coating station 18 has a humped cover 23 which is pivotallyraiseable about an axis 21 through about 90 degrees to the positionshown in broken lines at 22 in FIG. 1 by means of a hydraulic cylinder24 (see FIG. 4) which is power-operated with push-button control and isaided by a counterweight 26, to provide unrestricted access whennecessary to said station. The cover 23 rests on the bed 16 when in itslowered operational position illustrated in full lines in FIG. 1 so asto enable vapours produced by evaporation from the substance to becontained within the coating station 18, and is provided with glassinspection panels 28, areas of air inlet vents 30, and further air inletvents (not shown) in a small access door 32. The coating station 18 hasa base which is part of a continuous base 34 for the whole machine 10,walls 36 along its sides, and respective upstream and downstream baffleplates 38 and 40 across its ends in order to contain the vapours withinsaid station. The upper ends of the baffle plates 38 and 40 terminatejust below the bed 16 to form a shallow slot permitting feeding of thesheets therealong. The coating station 18 includes a housing 42 for areplaceable tank 44 from which the substance is supplied to saidstation. Doors 45 are provided in the wails 36 to allow access to thecoating station 18 when the cover 23 is raised in order to facilitatework on the machine by an operator. The sheet reject station 20 has aflat cover 46 which is pivotally raiseable about an axis 47 to theposition shown in broken lines at 48 in FIG. 1, to provide access whennecessary to said station, by means which are similar to those forraising the cover 23 but which are not shown because they are disposedon the other side of the machine 10. The cover 46 rests on the bed 16when in its lowered operational position illustrated in full lines inFIG. 1 so as to enable vapours produced by evaporation from thesubstance to be contained within the sheet rejection station 20, and isprovided with a glass inspection panel 50. The sheet reject station 20has a floor 52 disposed above the base 34, walls 54 along its sideswhich are continuations of the walls 36 of the coating station 18, anupstream baffle plate across one end constituted by the downstreambaffle plate 40 of the station 18, and a downstream baffle plate 56across the other end in order to contain the vapours within the station20. The upper end of the baffle plate 56 terminates just below the bed16 to form a shallow slot permitting feeding of the sheets therealong.Air inlet vents (not shown) are provided in a reject sheet withdrawaldoor 58 in one of the walls 54. As best seen in FIGS. 5 and 6, suctionmeans which are arranged to extract the vapours downwardly from withinthe working area 18, 20 include a duct 60 connected to the front zone ofthe base of the coating station 18, a duct 62 connected to the rear zoneof the base of said station, said zones being delineated by boundarywalls 64, a duct 66 connected to the housing 42 for the tank 44, a duct63 connected to the sheet reject station 20, and a duct 65 connected toa gearbox 71 for driving the machine 10. The suction means also includea suction fan 67 housed alongside the machine 10 which extracts all thevapours from the working area 18, 20 of the machine 10 downwardlythrough the aforesaid ducts into the base of the machine whence theypass through a common duct 69 into an upper zone of the oven 14 wherethey are incinerated. The suction fan is sufficiently powerful tomaintain a slight negative gauge pressure within the working area 18,20, which effectively draws in fresh air through the inlet ventshereinbefore referred to. However, as the concentration of vapourswithin the working area 18, 20 can be high because the operator is notexposed thereto, the requisite extraction flow rate is relatively lowthus providing high oven thermal efficiency and low running costs. Themachine 10 has front and rear platforms 68 and a hand-rail 70 for theuse of the operator, and is provided with a hoist 72 with a jib 74 forenabling machine elements to be changed. Said hoist is disposed abovethe working area 18, 20 and is completely unimpeded by the suction meanswhich are arranged to extract the vapours downwardly aided by the factthat said vapours are heavier than air. During setting and checking ofthe machine 10 when one or both of the covers 23 and 46 is or are raisedand the extraction system is still in operation, vapours are not drawnupwardly past the head of the operator but are safely drawn downwardlyinto the base of the machine.

In a modification, the working area of the machine comprises simply acoating station, no sheet reject station being provided.

What is claimed is:
 1. A sheet coating machine in which sheets are fedalong a bed through a working area where they are given a coating of avolatile substance to an adjoining oven where the coating is cured, atleast one cover which is moveable to provide access when necessary tothe working area and which enables vapours produced by evaporation fromthe substance to be contained within the working area, air inlet meanswhich enable the vapours to be extracted for incineration, and suctionmeans which are arranged to extract the vapours downwardly from withinthe working area.
 2. A sheet coating machine according to claim 1,wherein the working area comprises a coating station having a moveablecover which provides access when necessary to the coating station.
 3. Asheet coating machine according to claim 2, wherein the air inlet meansof the coating station comprise vents in the moveable cover.
 4. A sheetcoating machine according to claim 2 or claim 3, wherein the coatingstation is provided with a base, walls along its sides, and upstream anddownstream baffle plates across its ends in order to contain the vapourswithin the coating station, the baffle plates being adapted to permitfeeding of the sheets along the bed.
 5. A sheet coating machineaccording to claim 2 or claim 3, wherein the working area comprises alsoa sheet reject station disposed between the coating station and the ovenand having another moveable cover which provides access when necessaryto the sheet reject station.
 6. A sheet coating machine according toclaim 5, wherein the sheet reject station is provided with a floor,walls along its sides, and upstream and downstream baffle plates acrossits ends in order to contain the vapours within the sheet rejectstation, the baffle plates being adapted to permit feeding of the sheetsalong the bed.
 7. A sheet coating machine according to claim 6, whereinthe walls of the sheet reject station are continuations of the walls ofthe coating station, and the upstream baffle plate of the sheet rejectstation and the downstream baffle plate of the coating station are oneand the same element.
 8. A sheet coating machine according to claim 6,wherein the air inlet means of the sheet reject station comprise ventsin a reject sheet withdrawal door in one of the walls.
 9. A sheetcoating machine according to claim 1 or claim 2, wherein the suctionmeans which are arranged to extract the vapours downwardly compriseducts connected to the base of the coating station, to the sheet rejectstation, to a gearbox for driving the machine, and to a housing for areplaceable tank from which the substance is supplied to the coatingstation.
 10. A sheet coating machine according to claim 9, wherein theducts communicate with a common duct in the base of the machine leadingto an upper zone of the oven.
 11. A sheet coating machine according toclaim 1 or claim 2, provided with a hoist for enabling machine elementsto be changed which is disposed above the working area and is completelyunimpeded by the suction means which are arranged to extract the vapoursdownwardly.